Mailinglist Archive: opensuse (4570 mails)

["Steven T. Hatton" <hattons@xxxxxxxxxxxxxxxxxx>]

On Saturday 12 November 2005 07:34 pm, Randall R Schulz wrote:

> I'd think you'd not be given to folklore about program efficiency.
> Static compilation to native code as gcj (or conventional C++) does it
> is _not_ the best way to optimize performance. Java's so-called JIT
> (it's really on-demand) native code compilation has optimization
> opportunities not available when only static program analysis is
> possible.

I don't see how you can possibly achieve at runtime what a C++ compiler 
achieves.  First of all, you have to have the JVM running.  That, in itself 
is overhead.  There is no Class object in C++.  Templates don't exist at 
runtime.  You can write C++ in such away that you have very few pointers, and 
thus very little indirection overhead.  You simply cannot do that with Java.  
What a good C++ compiler produces from well written code is extremely lean.

> For all practial purposes and for a sizeable majority of programs, Java
> is every bit as fast as C++ and what's more, the opportunities for
> optimization of C++ are more played-out than are those for Java, which
> is still improving its performance characteristics.

GCC 4's C++ compiler produces significantly faster compile code than previous 
versions.  The new move semantics will continue to offer improvements.  
Furthermore, proper code design can have a profound impact on performance.

Steven